Fixing rigid inserts in flexible material

ABSTRACT

To achieve highly fluid-tight sealing of a rigid insert into an orifice in flexible material (101), the insert is made in two parts (103, 106) which can be pressed together with purely axial movement, one part deforming slightly relative to the other at least during the movement, until they adopt as a result of interengagement between them a relationship in which they exert a predetermined sealing pressure on the edge portion of the flexible material between their radially extending flanges (108, 109). A bead (102) may be accommodated in an oversize recess (122) in the flanges. A sub-assembly such as an eyepiece (111) is held fluid tight in one (103) of the parts. Detent means (107, 116) are designed to maintain a sealing contact even if the flexible material (101) or sealing ring (118) creep or set. Though the orifice has an endless edge it is not necessarily circular in outline.

FIELD OF THE INVENTION

This invention relates to the fixing of rigid inserts in an aperture inflexible materials.

BACKGROUND OF THE INVENTION

Such inserts may comparatively readily be fixed permanently bymoulding-in or permanent bonding, but when there is a requirement forremovability or replacability problems arise in achieving a fixing whichis at the same time fluid-proof and secure.

Such fixings have commonly been achieved by the use of spring clips orJubilee Clip type devices both of which are broken rings of which theends are drawn together--in the one case by the resilience of the ringmaterial itself and in the other case by a screw linkage joining them.In both cases there is an area of flexible material which is underlyingthe broken part of the ring where a seal is not assured and in the caseof the Jubilee Clip the tightening of the screw can cause distortion andcreep of the flexible material underneath the clip as a result of thepressures applied.

SUMMARY OF THE INVENTION

The present invention seeks to achieve fixing of a rigid insert housedin an orifice in a flexible material whereby substantially uniformloading of the flexible material all the way around the margin of theinsert is achievable without any necessary rotational movement betweenany of the parts involved. It is apparent therefore that the seal may beused around apertures which are not circular. In this specificationhowever, purely for convenience, the term "radial" and "axial" will beused to denote respectively "directions inwardly and outwardly of thecentre of the orifice" and "directions perpendicular to the generalplane of the orifice".

The insert includes a composite of two parts, the first part of whichhas a radially directed flange and an axially directed wall, the flangeof which is to lie over the flexible material. The other part of thering has a radially directed flange and an axially directed surfacewhich are respectively to over-lie the flexible material and to engageon the axial wall of the first part of the ring when the two parts arepressed in an axial direction together, thereby to squeeze axially themargin between the respective portions of the flexible material byvirtue of the axial approach of the two radial flange faces of the twoparts of the ring. Normally the insert will be supporting some elementwithin the orifice rather than merely acting as a boundary for theorifice; and that element may be integral with the insert.

The two parts may form a frictional force fit together and additionallyor alternatively may have detent means causing them to adopt a preferredaxial relationship. One or more of the wall and the surface may beslightly tapered so that upon axial approach of the two parts one of thetwo may be distorted slightly so as to compress radially the layer ofmaterial lying radially adjacent to the periphery of the insert. Bothparts are closed, endless, figures (not necessarily circular)corresponding to the outline of the orifice. The radial flange of onepart may overlie the flexible material over one face of a discrete saidelement mounted by the insert, and the radial flange of the other partwill overlie the flexible material over the opposite face of theelement, so that pressure is exerted on a composite of flexiblematerial/rigid element/flexible material by the two flanges. In thiscase, the flexible material into which the insert is secured ispreferably formed with a margin for the reception of the insert which isgenerally S-shape in cross-section.

In a preferred version however, the flexible material is trapped andaxially pressed directly between the flanges of the two parts.

In this version the radial flange and the radial surface may definetogether a constriction some distance from the axial wall. This forms acompartment with a reduced width slit opening around its radially outercircumference. With this embodiment the flexible material may have abead around its aperture located in the compartment and subjected inthat compartment to axial pressure while the material locatedimmediately (radially) outwardly of the compartment is pressed in theconstriction. Furthermore, there may be a further localized and radiallynarrow constriction exerted by a narrow ridge or lip on at least one ofthe flanges.

The insert is, in the present specific embodiment separate from theelement it is to support in the flexible material. That element may besecured to the insert in a way analogous to the attachment of theflexible material to the insert. The axial wall has a seat and detentmeans projecting radially from it. The radially outer edge of theelement is held between the stop and the detent by a third part, a ringwhich fits between the element and the detent, the detent beingundersize for the third part.

In many applications it is highly desirable to maintain a fluid tightseal between the flexible material and the element. A fluid tight sealwith the first and second rings is provided by the clamping of theflexible material between the first and second parts. Of course, if theelement is integral with one of the parts of the insert, that sufficesfor the purpose. But in order to seal the insert to a separate element asealing ring may be provided between the third part and the elementand/or between the element and the stop.

Since the parts are all complete, unsplit rings although they should bemade of a sufficiently stiff material to perform their fixing functionit is advantageous if one or more of them is made of a material having aslight resilience, such as nylon or a polyacetal (e.g. Delrin,Registered Trade Mark). In one embodiment to be described for examplethe third component is substantially less rigid than the first andsecond since it has to be squeezed past an undersize detent at a timewhen the axial flange of the first part is substantially deprived ofresilience by the positioning of the second part outside it. The morerigid ring(s) may, but need not, include reinforcing fibres. Theinvention has application to the retention of many different sorts ofelements in orifices in flexible materials but clearly is of greatervalue where a high degree of fluid-tightness and reliability are needed.

DESCRIPTION OF THE DRAWINGS AND OF PARTICULAR EMBODIMENTS

Particular versions of an application of the invention to the insertionof elements into a respirator will now be described with reference tothe accompanying drawings wherein;

FIG. 1 is a diametrical section through a first version showing thefeatures of the orifice of the flexible material and the parts of theinsert;

FIG. 2 is an enlarged partial view of FIG. 1;

FIGS. 3 and 4 are detailed radial section views of two parts of theinsert showing additionally detailed means on their inter-engagingportions;

FIGS. 5 and 6 are exploded and assembled scrap-sections of a secondversion; and

FIG. 7 shows in section a variant of the second version.

FIG. 1 shows two parts 1 and 2 of a composite insert engaged around themarginal portion 3 of a transparent rigid element 4 in this case a glasseyepiece of a respirator. The rubber material 5 of the respirator itselfforms a closed aperture into which the marginal portion 3 is fitted.

Looking now at FIG. 2, it can be seen that the aperture in the flexiblematerial 5 is defined by a generally S shape part when seen incross-section, a first loop 6 of the S being continuous with the body ofthe respirator proper. A first inlet 7 of the S is for receiving aplanar and generally radially directed flange 8 of the ring part 1 andthe second loop 9 of the S is for receiving the marginal portion 3 ofthe rigid element. The third loop 10 of the S removed from the body isacted against by the generally planar and radial flange 11 of thesecondary part 2. Although in a respirator the eyepieces are usuallycircular it is recalled once more that the invention is not restrictedto circular inserts and can be applied to inserts and orifices havingany closed configuration.

To compress the material of the end loop 10 of the S and also of itscentral loop 12 against the respective faces of the marginal portion 3of the element 4, the two ring parts 1 and 2 are forced axiallytogether, a movement which does not necessarily have any rotationalcomponent. This is achieved by providing on the ring parts axial walls13 and 14 respectively the radially inner face of one being forengagement in a force fit with the outer face of the other.

This force fitting may be achieved by a slight tapering of at least oneof the respective faces as indicated at 15 FIG. 2 which has also theeffect of a slight distortion of the inner of the rings in this case 13as the two parts are forced together thus applying also radialcompression to the material 16 lying radially outside the margin of theportion 3. Alternatively or additionally detent means can be used asseen in FIGS. 3 and 4. An annular bead 17 may be provided on one of theskirts for example skirt 13 of ring part 1 and one or more correspondingannular recesses at 18 on the skirt 14 of the ring part 2.

One of the ring parts preferably ring part 2 should be rigid andinextensible as possible being made for example of metal or plastics,possibly fibre-reinforced plastics. The inner ring will be ofsubstantially rigid material nevertheless having some compliance,examples being nylon or a polyacetal such as Delrin (Registered TradeMark). It will be seen that the rings when forced together form a closedframe around the outside of the element but do not touch it directly,compressing the flexible material evenly onto at least the axial facesof the element, avoiding stuffing, screwing or the setting up ofpotential leak paths.

The bead is fitted by first inserting the ring part 1 into the inlet 7of the S, placing the eyepiece in the second inlet 9 of the S and thenapplying the second ring part 2 to the first ring part 1 by a directaxial movement, preferably with a constant pressure tool. The use of aconstant pressure tool will ensure that if there are differences in sizeduring a given run of materials, the pressure achieved between rubberportions 10 and 12 and the marginal portions 3 of the insert will beconstant. This loading should preferably be such that the rubber in theloops 10 and 12 of the S is squeezed and displaced so that its thicknessis reduced by between 10 and 20% of its original thickness.

The ring part 1 preferably has--as shown in FIGS. 2 and 3 but not inFIG. 1--a further and radially outwardly directed flange 19. The reasonfor this is to allow the ready release of the seal by insertion of somelever such as a screwdriver between the flange 19 and the exposed end ofthe skirt 14 so that the two parts of the ring may be pushed axiallyapart. It is to be noted that this does not involve any contact betweenthe lever or tool and the flexible material.

A second and at present preferred version is seen in FIGS. 5 to 7.

In FIG. 5 the first of the ring parts 1' is a rigid hollow cylindricalsleeve in which an element such as a valve of filter may be mounted. Theradial flange 8' overlies one face of the edge 20 of the rubber materialof the face piece of a respirator. This may have a bead 21 to assistlocation and which assists in manufacture of the face piece in injectionprocessing), with an annular recess 22 in the flange 8' to accommodateit. Small ribs 23 on the edge 20 and narrow lip 24 in the flange mayassist totally air-tight sealing of the edge to the flange 8' and to theflange 11' of the ring part 2'. The axial surface 14' of that ring partis an interference fit with the axial wall 13' of the first ring part1', and location of the rings in an axially assembled condition seen inFIG. 6, where the rubber edge 20 is squeezed by about 10%-20% of itsoriginal thickness is assisted by detent means 17', 18', namely coactingrib 17' and recess 18' on the axial faces. The bead 21 is alsocompressed in the compartment formed by the recess 22.

Whereas ring 1' is as rigid and inextensible as possible, the ring 2' isof a more compliant material such as polyacetal as in the first version.Also as before, fitting of the rings is by a solely axial pressure,applied as evenly as possible to the ring 2' until it snaps ontoposition. To maintain a seal even if the rubber creeps or sets, theposition which would be adopted as a result of the interaction of thedetent means in the absence of any flexible material between the flangesis one of slightly closer axial approach than that which is actuallyachieved, even though the detent means are engaged, when the desireddegree of compression has been exerted on the flexible material betweenthe flanges. Thus, if there is any setting of the flexible material, therings will tend to approach closer and maintain a desired sealingpressure.

In the variant of the second version seen in FIG. 7, a flexible facemask of a respirator has holes for the insertion of rigid eyepieces. Atthe edge of each hole the material 101 of the face mask has a beadportion 102 of increased thickness. A first ring part 103 of an insertfor the holding of the eyepiece has an axially extending wall 104passing through the hole in the material 101 and a radially extendingflange 105 which overlies the material 101 adjacent to the hole. Theflange 105 is in this instance intended to be at that surface of themask which is nearer the wearer, though the opposite orientation isequally possible. The flanges and the wall are all endless (continuous).

A second ring part 106 overlies the material 101 on the other side fromthe radial flange 105. The second part 106 is restrained from movingaxially away from the radial flange 105 by an oversize detent 107 on theaxial wall 104 of the first ring 103. The second part 106 has no axialwall, but an axially extending inner peripheral surface.

The radial flanges 105 and 106 have opposed portions 108, 109 extendingtowards each other at a distance from the axial wall 104. This creates acompartment 122 for the bead portion 102 of the material 101 of the facepiece respirator. The compartment is slightly oversize for the bead sothat the latter may be deformed upon the exertion of axial pressure onit, when the parts are in a desired axial relationship, at which timealso the material 101 is pressed directly between the portions 108, 109and thereby sealed to them and held very securely. To increase thesecurity of the clamping and to further ensure a fluid tight sealbetween the material 101 and the first ring 103, the portion 108 of theradial flange 105 which extends towards the portion 109 of the secondring 106 has a radially narrow endless ridge 100 extending yet furthertowards the portion 109. The material 101 is locally compressed and/ordisplaced by this ridge 100.

The eyepiece 111 is secured to the first ring 103 in an analogousmanner, by a third ring component 112.

The first ring 103 has a stop 113 and a detent 114 extending radiallyinward from the wall and axially spaced from each other. The eyepiece111 is located against the stop 113, and is held in place by thepresence of the third component 112 which is restrained from movementaway from the detent 113 and the lens 111 by the undersized detent 14.

An O-ring 115 compressed between the lens 111 and the third ring 112ensures a fluid tight seal behind the eyepiece. Thus the aperture in theface mask is sealed overall in a fluid tight manner. The sealing ring115 could be replaced or supplemented by another resilient seal such asa gasket or packing between the lens and the third ring by a sealingring or gasket between the lens 111 and the stop 113.

With this construction the second part 106 is put in place by axiallydirected pressure with no rotation about the axis of the insert.Therefore this construction shares the advantage of the first version.The rigid eyepiece may be fitted by tilting it into one corner betweenthe stop 113 and the wall 104 and passing it over the diametricallyopposite portion of the detent 114, and the somewhat softer thirdcomponent 112 (e.g. of Delrin) can be forced axially past the undersizedetent after the attitude of the eyepiece has been chosen by rotatingit. This fixing does not require any complicated special shaping of theflexible material at the edge of the hole. In the example shown in thedrawing the insert does not protrude greatly on the inside of therespirator (the top side on the drawing) and has a bevelled profile, sothat it has a reduced tendency to irritate the wearer.

The eyepiece can be removed and replaced without detaching the first andsecond parts from the material. It is only necessary to remove the thirdring 112, which can be located on the outside of a respirator eyepiece,for easy access.

One advantage is some applications of locating the third ring on theoutside is that the force from any accidental impact on the outside ofthe eyepiece is transmitted directly to the integral stop in the firstcomponent, reducing the likelihood of the eyepiece being knocked out.

I claim:
 1. A rigid insert for fixing in an orifice which is bounded byan endless edge of flexible material, wherein the rigid insert has tworadially extending endless flanges, borne respectively on discrete partsof the insert, at least one of the parts having an axially extendingendless wall, the parts being constructed and arranged to be broughtinto an axial relationship wherein their flanges entrap between them andexert an axial pressure on at least an edge portion of the flexiblematerial by axial movement of one of the parts over the axial wall ofthe other, each part having an inclined surface, the parts then beingretained in that relationship by interengagement between the partsthrough interengagement of said inclined surfaces, one on each part andtending to establish a preferred relative axial position of the twoparts, the relative axial position being one of greater axial approachof the flanges than that at which the said axial pressure occurs.
 2. Aninsert according to claim 1, wherein the endless edge of the flexiblematerial is defined by a bead integrally formed of the material, and atleast one of the flanges of the parts includes an endless recess foraccommodating the bead while permitting axial compression of the bead inthe said axial relationship.
 3. An insert according to claim 2 whereinat least one of the edge portion of the flexible material and theflanges includes an endless radially narrow compression rib to applyover a narrow annulus a pressure in the flexible material greater thanthe said axial pressure.
 4. An insert according to claim 1 wherein theaxial wall of the insert lies radially within the edge portion of theflexible material and the flanges extend radially outwardly over thatedge portion, and one of the said parts is an integral portion of asubassembly occupying and sealing the orifice when the insert is sofixed.
 5. An insert according to claim 1, wherein the axial wall of theinsert lies radially within the edge portion of the flexible materialand the flanges extend radially outwardly over that edge portion, andone of the said parts provides a housing for a discrete subassembly, hasstop means against which the subassembly is to abut, and has compressionmeans for urging the subassembly in fluid tight manner against the stopmeans.
 6. An insert according to claim 5 wherein the compression meansincludes a resilient endless sealing ring against one face of thesubassembly, and a compression ring lodged against the inner peripheryof the axial wall to cause sealing engagement between the sealing ringand the subassembly.
 7. An insert according to claim 6 wherein thecompression ring is an endless ring engageable against the axial walland positioned by a endless detent to maintain it normal to the axis andto react against inward deformation of the axial wall.
 8. An insert asclaimed in claim 1 wherein at least one of said parts is slightlyresilient, and the fit of one over the axial wall of the other part is asnap fit over surface configurations permitting relative axial movementin engaging and disengaging directions under axial pressure sufficientto snap one part into or out of engagement with the other.
 9. A rigidinsert for fixing in an orifice which is bounded by an endless edge offlexible material, wherein the rigid insert has two radially extendingendless flanges borne respectively on discrete parts of the insert, atleast one of the parts having an axially extending endless wall, theparts being constructed and arranged to be brought into an axialrelationship wherein their flanges entrap between them and exert anaxial pressure on two thicknesses of an edge portion of the flexiblematerial which lie over both faces of an edge portion of a rigidsubassembly mounted by the insert, the edge portion of the flexiblematerial passing around the outside of that edge portion of thesubassembly, the parts being so brought into axial relationship by axialmovement by one of the parts over the axial wall of the other and thenbeing retained in that relationship by interengagement between theparts.
 10. In combination, a rigid insert mounted in an orifice in aflexible material, said orifice having an endless margin, and asubassembly mounted in said rigid insert, wherein said rigid insertcomprises two parts each having a radial flange and at least one of saidparts having a continuous axial wall, the margin of said flexiblematerial being compressed between said flanges, one of said parts beingpenetrated by the said axial wall of the other of the parts andinterengaging means on the parts holding said parts in an axialrelationship exerting the compression, at least one of said parts beingslightly resilient, the fit of one part over the axial wall of the otherpart being a snap fit over surface configurations permitting relativeaxial movement in engaging and disengaging directions under axialpressure sufficient to snap one part into or out of interengagement withthe other, said subassembly being mounted radially within saidpenetrating axial wall and retained axially by a second flange on saidpart having said axial wall, said second flange projecting radiallyinwardly of said wall, and a retaining ring radially within said walland interengaging therewith to exert compression on said subassemblyagainst said second flange, said retaining ring being softer than theother parts, the interengagement of said interengaging means and of saidretaining ring with said wall being effected without requiring relativerotation as would be necessary for screw threaded interengagements. 11.The combination of claim 10 wherein a sealing ring is engaged between atleast one face of the subassembly and one of the members between whichit is retained.
 12. The combination according to claim 10 wherein saidinterengements of said parts and of said retaining ring with the saidwall are through respectively inclined surfaces urging saidinterengagements in a direction of increased compression.
 13. Thecombination as claimed in claim 10 wherein said retaining ring isslightly resilient and is a snap fit with said wall over surfaceconfigurations permitting relative axial movement in engaging anddisengaging directions under axial pressure sufficient to snap theretaining ring into or out of interengagement with the wall.
 14. Amethod of fixing a rigid insert within an orifice which is bounded by anendless edge of flexible material wherein the rigid insert has tworadially extending endless flanges borne respectively on discrete partsof the insert, at least one of the parts having an axially extendingendless wall, comprising bringing the parts into an axial relationshipwherein their flanges entrap between them and exert an axial pressure onat least an edge portion of the flexible material by axial movement ofone of the parts over the axial wall of the other, and retaining theparts in that relationship by interengagement between mutually inclinedwalls on the said parts whereby the flanges continuously tend to beurged toward each other and to be located closer to each other than atleast initially permitted by the flexible material.
 15. A method offixing a subassembly into an orifice which is bounded by an endless edgeof flexible material by using a rigid insert, wherein the rigid inserthas two radially extending endless flanges borne respectively ondiscrete parts of the insert, at least one of the parts having anaxially extending endless wall, comprising bringing the parts into anaxial relationship wherein their flanges entrap between them and exertan axial pressure on an edge flange of the subassembly through twolayers of an edge portion of the flexible material which is wrappedaround the outside of the edge flange, by axial movement of one of theparts over the axial wall of the other and retaining the parts in thatrelationship by interengagement between them.